Multi-analyte reference solutions

a reference solution and multi-analyte technology, applied in the field of reference solutions for instruments, can solve the problems of difficult to formulate aqueous solutions with physiological, difficult to maintain tolerable interference levels, and relatively unstable blood products, etc., to achieve the effect of not being highly viscous and maintaining tolerable interference levels

Active Publication Date: 2008-09-09
INSTR LAB
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Benefits of technology

[0007]The present invention provides a reference solution for use in instruments that determine hematocrit levels in biological samples by measuring the conductivity of the biological samples. A reference solution according to the invention achieves conductivities representative of known hematocrit levels in blood, while maintaining tolerable levels of interference with the measurement of other analytes in the reference solution. In addition, a reference solution according to the invention is not highly viscous, does not form a precipitate during shipment or storage, and is more stable at room temperature than reference solutions that contain blood products. A reference solution according to the invention can be used to simultaneously calibrate an instrument that analyzes biological samples for hematocrit and biological analytes.

Problems solved by technology

However, blood products are expensive, must be refrigerated during shipment and storage, and are relatively unstable.
However, it is difficult to formulate an aqueous solution with physiological levels of biological analytes (such as sodium, for example) and hematocrit in the same solution, because an aqueous environment that lacks red blood cells is far more conductive than whole blood.
However, large amounts of additives can drive up the cost of the reference solution, particularly in the case of relatively expensive inert particle additives.
In addition, high concentrations of additives can lead to unwanted side-effects, including interference with other analytes in the reference solution, high viscosity, reduced shelf life, and precipitation during shipment and storage.
Furthermore, certain water-soluble chemical additives can permeate some sensors within the blood analyzer (such as an oxygen sensor, for example) and reduce the sensitivity and selectivity of the sensors.
Because of these problems, existing reference solutions cannot effectively calibrate a blood analyzer for both hematocrit and biological analytes simultaneously.
As a result, at least two separate reference solutions must be used to calibrate a blood analyzer, which reduces the overall speed and increases the cost of operating such instruments.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0045]A reference solution was formulated according to Table 1 below:

[0046]

TABLE 1Deionized Water1.00 LHEPES buffer 100 mmolNaOH  75 mmolNaCl  80 mmolKCl 7.0 mmolCaCl21.00 mmolChloline Chloride  1 mmolGlucose  12 mmolLithium Lactate  4 mmolMIT biocide 2.0 mmolFD&C Blue No. 10.01 gFD&C Yellow No. 50.03 gPEG (MW 2000)  90 gDextran (MW 10,000)  60 gEthylene Glycol  90 g

[0047]The reference solution was introduced to a blood analyzer containing an electrode card equipped with sensors to detect pH, carbon dioxide (CO2), oxygen (O2), sodium (Na), potassium (K), calcium (Ca), glucose (Glu), lactate (Lac), and hematocrit (Hct). Three hematocrit values were obtained, along with three concentration values for each analyte. After the final measurement, the electrode card was replaced and the procedure was repeated with a new electrode card containing the same type of electrodes. In some instances, two measurements were recorded with each electrode card, and in others one measurement was recorde...

example 2

[0049]A reference solution was formulated according to Table 2 below:

[0050]

TABLE 2Deionized Water1.00 LHEPES buffer 100 mmolNaOH  66 mmolNaHCO3  20 mmolNaCl  68 mmolKCl 7.0 mmolCaCl21.00 mmolChloline Chloride  1 mmolGlucose  12 mmolLithium Lactate  4 mmolMIT biocide 2.0 mmolFD&C Blue No. 10.01 gFD&C Yellow No. 50.03 gPEG (MW 2000) 130 gDextran (MW 10,000) 100 gEthylene Glycol  70 g

[0051]To predict the room temperature stability of the solution, accelerated stability studies were performed as described below.

[0052]The reference solution was introduced to a blood analyzer containing an electrode card equipped with sensors to detect pH, carbon dioxide (CO2), oxygen (O2), sodium (Na), potassium (K), calcium (Ca), glucose (Glu), lactate (Lac), and hematocrit (Hct). Twelve hematocrit values were obtained, along with twelve concentration values for each analyte. The average of these values is reported in the time=0 row of FIG. 4.

[0053]Aliquots of the solution were stored at 5° C., 25° C., ...

example 3

[0057]A reference solution was formulated according to Table 3 below:

[0058]

TABLE 3Deionized Water1.00 LHEPES buffer 100 mmolNaOH  44 mmolNaHCO3  20 mmolNaCl  58 mmolKCl 3.0 mmolCaCl22.00 mmolChloline Chloride  1 mmolGlucose  3 mmolLithium Lactate 0.8 mmolMIT biocide 2.0 mmolFD&C Blue No. 10.05 gPEG (MW 2000)  90 gDextran (MW 10,000)  60 g

[0059]Accelerated stability studies on the solution were conducted as described above. First, aliquots of the solution stored at 5° C. and 25° C. were tested as above at 4, 6, and 12 weeks. The results of this study are summarized in FIG. 5. After 12 weeks, no appreciable change in hematocrit and analyte concentration values were recorded, so the test was halted. New aliquots of the solution were placed in ampoules and pasteurized. An accelerated stability study was performed, as described above, on aliquots stored at 5° C., 35° C., and 45° C. After 4 weeks, no appreciable change in hematocrit and analyte concentration values were recorded, as shown...

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Abstract

The present invention provides a reference solution for use in instruments that determine hematocrit levels in biological samples by measuring the resistance and / or conductivity of the biological samples. A reference solution according to the invention achieves conductivities representative of known hematocrit levels in blood, while maintaining tolerable levels of interference with the measurement of other analytes in the reference solution.

Description

TECHNICAL FIELD[0001]The present invention relates to the field of reference solutions for instruments that measure analytes in biological samples, particularly to instruments that determine hematocrit levels in biological samples by measuring the resistance and / or conductivity of the samples.BACKGROUND INFORMATION[0002]In the past, it was customary for clinical chemists to measure biological analytes in serum or plasma by flame photometry, coulometry, or fluorometric titration. Hematocrit, the percentage of blood volume occupied by cells (also known as packed cell volume), is measured in whole blood by micro-centrifugation or cell counting. More recent advances in clinical instrumentation have allowed for simultaneous measurement of biological analytes and hematocrit in a single sample. One type of modern blood analyzer measures biological analytes (such as sodium, for example) by direct potentiometry and hematocrit by conductivity. These instruments vastly improve the speed at whi...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G01N31/00G01N33/96G01N33/487G01N33/49
CPCG01N33/4915G01N33/492G01N33/96Y10T436/101666Y10T436/108331Y10T436/106664Y10T436/102499Y10T436/104998Y10T436/10
Inventor CONLON, DENNIS ROBERTMANSOURI, SOHRABVAGO, GIANNANTONIO
Owner INSTR LAB
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